Ideally you want an ambient (room) temperature of 80 to 85 degrees, if you watch some of the breeder interviews on youtube you will hear almost all of them say the ambient air temp is set to 82 degrees. It is ok if this temp drops down to high 70's during the night, say 77 or 78 degrees. These temps will also be the suggestion for the cool side hide in the tank or tub. For the hot side hide most will try to keep the temp at 88 degrees though it's ok if this goes up to as high as 95 degrees though most tend to stay lower say around 90 degrees. I wouldn't let the hot side temp drop below 88 degrees even at night, you want this to stay pretty constant as it's where the snake will go to digest a meal and the more stable the temp the better it is for digestion. If you provide a warm side and a cool side hide area then the snake will decide where he wants to be you shouldn't have to be changing the temps between the two zones just because it's night time.

Hope this helps.

BTW this info comes straight from Kevin McCurley's book Ball Pythons in Captivity.